Edit: Just noticed that we have the same mobo. I'd recommend flashing your bios everytime you make changes to it to avoid the Asus bios bug. When the bios bug hits you your CPU and mem won't be stable at ANY settings. I learned it the hard way when I almost RMA'd my RAM.

Not to derail too much, but what is this bios bug... I've been spending more time lately with other people's pcs than my own, but have never had an issue with any of the bios on my p8z77 v pro (knock on wood)

I did a quick Google search and the most I turned up was some people frying chips and or ram from what seemed more like user error and another few people that had their settings and profiles wiped due to some erroneous code that only happened when it failed to boot directly after an oc, but I'm pretty sure Asus has already fixed so nice then...

So just curious as to what it is so I can avoid it if it's something else I just haven't heard about.. That said flashing the bios every time you change a setting seems like it would be a real pain in the butt.

I neither know much about it. I only know that flashing is the only way to fix it. It seems to trigger randomly. The last time when I searched info about it was over a year ago and even then it was hard to find any info as it seems to be a rare issue. Nowadays the board is kind of old so the discussions about it must be really hard to find. Heck, it might only happen with a specific hardware combo like IVB + Corsair Vengeance mem as it seems to be the only thing my PC and OP's pc have in common.
All I know that from my experience it is a real issue and it must not be caused by a defective mobo as I'm on my 2nd p8z77-v pro and it still happened at least once. It could be fixed in the newest bios update or not. Hard to say because the changelog only states this: "Improve system stability.". I've kept reflashing just to be sure that it really is my CPU that is unstable when I don't pass a stress test.